Machsupport Forum
Mach Discussion => Mach4 General Discussion => Topic started by: jbraddock on June 24, 2018, 07:59:36 PM
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error message as soon as its starts to cut it stops an throws this error....
>>>Clearing a spurious limit hit latch event, Start logging in menu Diagnostic Logging to see more detail,....<<<<
i tried that diagnostic logging... i belive i did... if im in right area,... an i didnt tell me anything unless im not using it right,.....i thought maby my motors are moving to fast so i turned them down... same error, works if i cut air but the min i start cutting aluminum it throws this error,....im at a lost as what its referring too??? its like it knows it is cutting but it never lets me go any farther than the start ofo , the cut, im going slow as possible but same error..????wth???
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Hi,
sounds like electrical noise, almost certainly from your spindle, propagating to one or more
of the limit switch circuits.
Are you using Mach3 or Mach4?
You could try increasing the de-bounce in Mach3 or increase the filter time in Mach4.
Craig
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Hi,
the spindle really starts producing noise as it comes under load....ie cutting.
What kind of spindle and spindle drive do you have?
Craig
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IM Using a kbmm 225d with a tread mill motor,... on mach 4, i have tried 3 diffrent plugins as well, its been throwing limit switches errors as well
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Hi,
that speed control is fairly noisy, its a phase controlled bridge rectifier.
As an experiment try plugging your speed control into a different (different circuit)
than your PC and CNC machine. It may be that the noise transferred back into the mains
is getting into your machine.
Other than that you are going to have to filter both input and output of your speed control.
Have you tried increasing the filter time in Mach4? Stopping the speed control from producing noise
is the best solution. Increasing the filtering on your signal (limit) lines is often effective but not the first
line approach.
Craig
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My motor speed controller is plugged into s different outlet, how do you filter input an outputs in mach 4,? Also im not running my speed control through mach 4, im using the speed control knob an power switch, i havent added spindle control to mach yet,...i did notice without limit switches on it doesnt do it... i re routed my wires to limit switches but it didnt change anything
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Hi,
the electrical noise is being generated by the speed controller and your spindle motor.
It is being radiated to your signal lines in your machine. They are sensitive. A big
noisy (electrically) motor running right next door will induce small voltages and currents in signal
lines close by.
You can jump up and down and blame Mach if you wish but it wont do you any good, this is
physics...you could blame James Clerk Maxwell (1831-1879), the 'father' of electromagnetics...
but hes just a little bit dead at the moment!
Good practice put all the high power lines like your spindle wires as far away from Machs signal lines as possible.
The next best practice is to put filters on the input and output of your speed control. If you have
a VFD you MUST follow manufacturers recommendations or you will blow your VFD up.
Your speed control is very much less high tech and good line filters will help a great deal without risking
your speed control.
The next technique is to reduce the sensitivity of the signal lines to electrical noise. If you have a look on
the ESS Config plugin, Pins page you will see that inputs have a filtering setting. Try putting a setting of 100
say in each of your limit switch inputs. It may help.
Best practice is to prevent your speed control generating noise ie line filters, next best is reducing the coupling
of noise into your signal wiring, ie physical separation and screening, the next best is introduce filtering on the inputs,
ie the software filter I've mentioned and/or RC low pass filters on the pins.
Craig
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Hi,
this sort of thing:
http://nz.element14.com/schaffner/fn2020-20-06/filter-20a-chassis/dp/1191370 (http://nz.element14.com/schaffner/fn2020-20-06/filter-20a-chassis/dp/1191370)
Ideally one on the input and it wouldn't hurt to have one on the output too.
Craig
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To the OP
Do you have all the equipment equipotentialy bonded with at least a wire of 6mm csa
You need a good odd order harmonics filter fitted to your spindle drive input it the 9th harmonic that does the damage
All low level signal cables should be shielded with the braid only bonded at one end
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As Craig mentioned the first line of attack should be physical separation and shielding, especially for the power leads from the speed control to the motor.
The filter recommended by Craig may work for a phase angle controller for DC motors such as the KBMM but beware using them for a VFD.
VFD's generate high levels of harmonic current and generic noise filters may not survive usage on a VFD, especially on the output because the internal capacitors may overheat. In that case I would recommend instead that you put a generic filter, such as the one that Craig recommended in the link above, on the input power for the control board and the host computer and monitor. Then put a large simple ferrite ring common mode choke on the output and possibly the input of the VFD.
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Hi,
Steve's 100% if you have a VFD....don't use ordinary line filters, they wont work and may cause more problems than they solve.
Most manufacturers specify 'line reactors' on the input side of a VFD, not filters at all. Most manufacturers recommend NO output filtering on the output side UNLESS there
is a big (30m plus) cable run between the VFD and motor. Even then the filters are specialized....ordinary line filters will not do it.
Craig
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We use Line Reactors from Automation Direct and have had very good results.
We filter our VFDs and Servo Drive input power through line reactors.
https://www.automationdirect.com/adc/Shopping/Catalog/Drives/AC_Drive_(VFD)_Spare_Parts_-a-_Accessories/AC_Line_Reactors
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Hi,
in this instance OP is using a phase controlled bridge rectifier for a DC output. In that case line reactors are the exactly wrong choice,
excess line inductance makes it ever harder for SCRs to commutate. Ordinary line filters on input and output result in noise reduction
without designing specialist filters.
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Agreed, putting line filters between a SCR phase angle DC drive and a DC motor is not a good idea. Using a shielded cable could still be helpful.
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Hi,
I'm not so sure I agree with you Steve, I regularly put filters between a phase controlled bridge and
its DC load.
The input capacitance is typically less than 1uF and therfore the dV/dt current at AC line frequencies is
pretty modest. The capacitance is useful in reducing HF ringing on the DC output line.
One of my recent projects involved a phase controlled bridge delivering spot weld current, low voltage to be
sure but about 20kA! I fitted filters at the input of the transformer AND the output of the bridge. The inductor
was 95mm sq weld cable wrapped around a laminated core.
Craig
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I am confused. You stated that reactors could be a problem for SCRs trying to commutate. Line filters contain reactors (inductors) and would have this same effect. Perhaps it is a matter of the size of the inductor in a "filter" being smaller than a "line reactor"?
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Hi Steve,
exactly, line filters have inductances usually less than 500uH whereas line reactors in usually in excess of 5mH.
Line inductance causes the current to lag voltage, so as the current falls to near zero, the point at which the SCR would
commutate the voltage has already increased from zero. So just at the moment that the SCR has to establish its
reverse block its already under dV/dt stress.
Almost all VFDs have a rectifier/capacitor input which causes line current to be drawn in short duration high current pulses at the
peak of the voltage excursions. It causes current 'distortion' on the line, much to the power companies disadvantage.
Line reactors cause the pulses to be of longer duration and lower peak values with reduced current distortion. In many
cases the power companies will mandate that they be fitted on large installations.
While both line filters and line reactors are for the benefit of the electrical supply they address different technologies.
Craig
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shield ,shield ,shield ,both side inverter and motor
if you use pokeys hardware be sure you use the gndi not gnd
i used many controllers types in pokeys the noise problem are solve much faster than other thanks for that gndi
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Its doing same error, without motor even powered on,...now
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Its doing same error, without motor even powered on,...now
Whats gndi? I am using pokeys, is that gndi in pokeys or ess? Right now until i get problem figured out i got pokeys unhooked, i use pokeys for jog joystick, ground going to each pokey pin to activate joy stick axis,....but as i said i unhooked it til this issue is sorted out
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Hi,
have you tried increasing the filtering time in the ESS plugin?
Craig
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yes it got worse when i plugged in the minimum it says in info tab is 1.8441 in description, it locks up an crashes mach when i try values,.... im now getting ERROR,..."CANT TRANSITION FROM MDI RUNNING TO STOP" once im referenced an have my zeros ...i hit go to work zero an it throws cant transition mdi error,...i belive my ess must be bad its like its confused, it try an gos up instead of down when it throws that error,
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im cutting,... finally.... BUT with home switches only......, had to turn off all limits IN ESS,...STILL USING ESS HOME SWITCHES WHICH ARE THE SAME SWITCH AS LIMITS,...AN PIN #S...??? i think i got a bad card??
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Hi,
its possible that its bad but more likely you have a noisy setup affecting limits and your probe.
To what have you set the filtering on the different inputs?
Craig
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Hi,
the reason noise on the home switches doesn't affect the machine as badly is that Mach ignores
homes EXCEPT when homing. It monitors limits at all other times and therefore noise will cause Mach
to Estop whereas the homes wont.
Craig
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HOW Far should power supply an ess be away from each other
,.. mine are right ontop of each other..? im cutting now so il get you my filter figures later
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Hi,
its possible that its bad but more likely you have a noisy setup affecting limits and your probe.
To what have you set the filtering on the different inputs?
Craig
any fifgures was crashing my ess configurator,... it wouldnt let machine move, it would crash as soon as i tried to open a change to a diffrent setting in noise filters
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Hi,
its possible that its bad but more likely you have a noisy setup affecting limits and your probe.
To what have you set the filtering on the different inputs?
Craig
probe..? im not using one that i know of unless your talking a bought something that idk, WHICH IS VERY POSSIBLE.... im using a wobbler if that is what you mean, im not using a touch probe..???
is that what you mean by probe A TOUCH PROBE..????
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Hi,
sorry, I thought you were using an electric touch probe.
Have you installed line filters on your spindle?
Have you shielded the input and output wires of your spindle?
Have you shielded the limit switch wires?
Have you introduced any filtering on the input signal lines, either programaticaly or an RC low pass filter?
Craig
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Hi,
sorry, I thought you were using an electric touch probe.
Have you installed line filters on your spindle?
Have you shielded the input and output wires of your spindle?
Have you shielded the limit switch wires?
Have you introduced any filtering on the input signal lines, either programaticaly or an RC low pass filter?
Craig
no.... it doese this with out motor even powerd on so that tells me its not a spindle motor or speed controller problem
no
yes
tried an it made worse an crashed everytime if by filtering you mean through ess on inputs
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Hi,
tried an it made worse an crashed everytime if by filtering you mean through ess on inputs
This is wrong somehow, there is no way increasing a filter time constant on an input should do that.
Have you electrically bonded all the metal parts together?. It sounds to me like you may have a power
supply issue or alternately some leakage current into the frame of the machine.
Try unpluging the spindle speed control from the AC line. If the motor has poor isolation it will
have leakage current into the frame of the machine and will very very easily overwhelm computer level
signals.
Craig
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Hi,
this is probably a bit off topic but here goes.....
I have stated that a VFD often requires line reactors, essentially high inductance filters to accommodate the current pulses that occur in the rectifier/capacitor input circuit.
I have attached two pics, one of the rectifier/capacitor circuit (representative) and its output voltage. Note the ripple on the DC. The second pic is the Fast Fourier Transform (FFT)
of the output voltage waveform. Note the spectral components at the 2nd, 4th, 8th and 10th harmonics. Low order harmonics like this require a highly inductive filter because of the low
frequencies involved.
I have also stated that a phase controlled bridge such as OP is using is noisy and requires line filters capable of filtering higher frequencies. Accordingly I have attached another two pics,
the first a circuit of a phase controlled bridge rectifier (representative). Note that the gate drive voltage sources are low voltage pulses to turn the SCRs on. The output voltage of the bridge
is also shown. Now look at the second pic being the FFT of the output voltage. Note how the harmonic distortion extends all the way out to over 100kHz.....noisy as hell!
Craig
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The last fft certainly gives a graphic indication of how those sharp edges translate into the frequency domain. As you say, it is an aside since the op says it isn't RFI from the spindle drive, but it's interesting to see anyway.
Allan
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Hi Allan,
yes its quite dramatic.....when I was cropping the screenshot to post I inadvertanly cut off the frequency scale off the bottom of the FFT pic.
The full picture showed significant harmonic energy to 100kHz and certainly measureable out to 1MHz.
I suspect that OP will find that the speed control is still at the root of his problems, whether he knows it or not. What else can produce the sort of hash this speed control
produces?
One feature of this speed control is that the DC produced is not isolated from electrical earth, at least in New Zealand where we have a MEN electrical system. That means
that the insulation resistance of the motor OP is using is the only thing which prevents line level voltages from getting into the frame of the machine. Additionally there
is a good possibility of the so called, and dreaded 'homopolar' current.
The 5 phase steppers I use on my mill are subject to this phenomenon. They have good insulation to the frame as measured by a Megger. The drivers are direct feed from the AC
mains to a DC link voltage of 150VDC. The magnetic coupling between the stepper coils and the frame mean there is leakage to the frame, several mA at least. Without earth bonding I have
measured 130V on the frame of the machine......a great surpise to me I can tell you. I have investigated quite thoroughly and it turns out the voltage induced into the frame
is in the kHz range, ie phase switching frequency so the current is induced in the frame rather than resistive leakage.
Homopolar current is not common, there is little mention of it in the literature and that is seems to fly in the face of Kirchoffs Law its little wonder that it gets missed. That's what happened to me
anyway!
Craig